Studies on the System Nitric Acid―Water―Tri-n-butyl Phosphate

Abstract

It is intended in this study to determine the composition of species formed in the equilibrated organic phase and to clarify the extraction mechanism in the system of HNO₃-H₂O-TBP. Similarly as the previous papers on the systems of mineral acid-H₂O-TBP, physico-chemical measurements of volume swelling, density, viscosity and electrical conductivity were carried out on the equilibrated organic phase, in addition to the conventional distribution measurement of HNO₃ and water between organic and aqueous phases. It was found that the major extracted species are (TBP)₂·HNO₃·H₂O and (TBP)₂·H₂O·H₃0⁺···NO₃－ in the medium acidity region and TBP·HNO₃ and TBP·HNO₃·H₃O⁺··· NO₃－ in the higher acidity region. Apparent degree of dissociation in the organic phase is below 0.05 over the whole range of nitric acid concentration studied, and the extracted species are almost undissociated or ion-paired.